Carbide-modified erosion-resistant alloy steel, method of making and use thereof

Abstract

The application discloses a carbide modified abrasion-resistant alloy steel and a preparation method and application thereof, and relates to the technical field of wear-resistant steel. By adding a higher Cr element and combining with the addition of a proper amount of C element, the solid solution strengthening effect of the steel and the precipitation of hard chromium-containing carbides are ensured, which is beneficial to the improvement of the wear resistance of the steel. In addition, by controlling the addition amount of the C element, after the precipitation of the carbides, part of the carbon still exists in the matrix, which promotes the final formation of hard and tough lath martensite and avoids the generation of high-carbon brittle acicular martensite. Moreover, by adding the higher Cr element and proper amounts of Ni and Mo elements, the steel can still maintain a passivation state in a weak acid corrosive environment, so that the corrosion resistance of the steel is increased. Furthermore, V, Zr and Re in the steel can also react with C to precipitate carbides in the matrix, which can effectively control the size of the carbides, so that the wear resistance of the steel is ensured while the toughness and corrosion resistance of the steel are not damaged.

Description

Technical Field

[0001] This invention relates to the field of wear-resistant steel technology, and more specifically, to a carbide-modified wear-resistant and corrosion-resistant alloy steel, its preparation method, and its application. Background Technology

[0002] Wear-resistant steel is widely used in basic industries such as mining, metallurgy, petrochemicals, power, dredging, and marine engineering, and is a core component material for engineering machinery equipment. With the continuous expansion of applications for wear-resistant steel, such as in the operating environments of wet semi-autogenous grinding / ball mills, pumps, pipelines, impellers, and cutter teeth, the performance requirements for its manufacturing materials are higher due to the presence of corrosive media in these environments. Therefore, it is necessary to select or develop wear-resistant and corrosion-resistant steels that combine both wear resistance and corrosion resistance.

[0003] Traditional wear-resistant materials include high-manganese steel, low-alloy steel, and wear-resistant cast iron. However, these materials all have at least one drawback, such as insufficient corrosion resistance, insufficient wear resistance, relatively low hardness, low toughness, or difficulty in meeting the service requirements of high-impact conditions. It is difficult to obtain alloy steel that combines high hardness, high toughness, and corrosion resistance.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a carbide-modified wear-resistant alloy steel, its preparation method, and its application.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a carbide-modified wear-resistant alloy steel, comprising, by mass percentage: C: 0.27–0.34%, Mn: 0.4–1.0%, Cr: 8.5–11.5%, Si: 0.6–1.0%, Ni: 0.3–0.8%, Mo: 0.3–0.8%, V: 0.1–0.35%, Zr: 0.01–0.06%, Re: 0.02–0.06%, N≤0.015%, S≤0.03%, P≤0.03%, with the balance being iron and unavoidable impurities.

[0008] Secondly, the present invention provides a method for preparing carbide-modified wear-resistant alloy steel as described in any of the foregoing embodiments, comprising melting raw materials of C, Mn, Cr, Si, Ni, Mo, N, S, P and Fe into molten steel in proportion, then adding raw material of V in proportion for a first melting modification, then adding raw materials of Zr and Re in proportion for a second melting modification, after the two melting modifications are completed, casting the molten steel into a casting, and then heat treating the casting.

[0009] In a third aspect, the present application provides a use of the carbide-modified erosion-resistant alloy steel according to any one of the preceding embodiments or the preparation method according to any one of the preceding embodiments in the field of improving corrosion resistance or friction resistance of equipment.

[0010] The present application has the following beneficial effects:

[0011] The present application provides a carbide-modified erosion-resistant alloy steel and a preparation method and use thereof. By adding a higher amount of Cr element and combining with the addition of an appropriate amount of C element, the solid solution strengthening effect of the steel and the precipitation of hard chromium-containing carbides are ensured, which is conducive to the improvement of the wear resistance of the steel. In addition, controlling the amount of C element added can ensure that part of the carbon remains in the matrix after the precipitation of carbides, promote the final formation of hard and tough lath martensite, and avoid the generation of high-carbon brittle needle-like martensite. Furthermore, the addition of a higher amount of Cr element and appropriate amounts of Ni and Mo elements can effectively ensure that the steel can still maintain a passivation state in a weakly acidic corrosive environment, thereby increasing the corrosion resistance of the steel. Still further, V, Zr and Re in the steel can also react with C to precipitate carbides in the matrix, which can effectively control the size of the carbides, ensuring the wear resistance of the steel while not damaging its toughness and corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0013] Figure 1 Scanning electron microscope image of the carbide-modified erosion-resistant alloy steel provided for Embodiment 1 of the present application. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained by market purchase.

[0015] The features and properties of the present application will be further described in detail below in combination with the embodiments.

[0016] With the continuous expansion of the application field of wear-resistant steel, the performance requirements are also increasing. Not only is it required to have good mechanical properties, such as high strength, good wear resistance, impact resistance, etc., but also to have good corrosion resistance. However, traditional wear-resistant materials, such as high manganese steel, low alloy steel, wear-resistant cast iron, etc., cannot meet all the above requirements. Therefore, the inventors propose the following solutions.

[0017] In a first aspect, the present application provides a carbide-modified wear-resistant alloy steel, which comprises, by mass percentage, C: 0.27-0.34%, Mn: 0.4-1.0%, Cr: 8.5-11.5%, Si: 0.6-1.0%, Ni: 0.3-0.8%, Mo: 0.3-0.8%, V: 0.1-0.35%, Zr: 0.01-0.06%, Re: 0.02-0.06%, N≤0.015%, S≤0.03%, P≤0.03%, and the balance being iron and unavoidable impurities.

[0018] The effects of each element on performance are as follows:

[0019] C: Carbon is one of the most basic elements in steel, and its existence in steel organization includes solid solution into the matrix and precipitation of carbide, etc., which is a key element affecting the mechanical properties, corrosion resistance and wear resistance of steel materials. In order to ensure that the matrix organization is a good toughness lath martensite and a certain amount of hard carbide precipitates, the carbon content is controlled in the range of 0.27-0.34%.

[0020] Mn: Manganese is an important element for stabilizing austenite structure, and can also play a role in solid solution, deoxidation and desulfurization, but excessive addition will affect the weldability and toughness of the steel. In order to ensure a lower oxygen content, sufficient hardenability and certain work hardening capacity in the alloy steel, the manganese content is controlled in the range of 0.4-1.0%.

[0021] Cr: Chromium is an important element affecting the mechanical properties and corrosion resistance of steel materials. The solid solution of Cr and the carbide precipitated by combining with C can effectively improve the wear resistance of wear-resistant steel, but the carbide formed by Cr is easy to grow, which reduces the toughness of the wear-resistant steel. At the same time, Cr can improve the hardenability of steel and bring good corrosion resistance to steel materials. In order to ensure the hardenability of the alloy steel, precipitate enough hard carbide in the organization to improve the wear resistance, and keep the steel surface passivated in the corrosive medium to improve the corrosion resistance, the chromium content is controlled in the range of 8.5-11.5%.

[0022] Si: Silicon is one of the deoxidizing elements of steel, which has a certain solid solution strengthening effect and can appropriately improve the corrosion resistance of alloy steel. The content of silicon is controlled in the range of 0.6-1.0% in the present application to ensure that the oxygen content of the molten steel is qualified.

[0023] Ni, Mo: both nickel and molybdenum have the effect of improving the strength, corrosion resistance and hardenability of the steel. In addition, the nickel element can improve the weldability and low temperature toughness of the steel, and the molybdenum is beneficial to improve the tempering stability of the steel. The present application comprehensively considers the material cost and the demand of thick and large wear-resistant parts, and controls the content of nickel and molybdenum in the range of 0.3-0.8%.

[0024] V: vanadium can be dissolved in the austenite of the steel at high temperature, play a solid solution strengthening effect, at the same time can refine the organization and grain of the steel, easy to generate carbide in the steel. The present application utilizes the addition of vanadium element to play the role of carbide modification, considering its solid solution in the matrix structure and the possible promotion of carbide growth, the content is controlled in the range of 0.1-0.35%.

[0025] Zr and rare earth Re: both zirconium and rare earth elements are strong deoxidizing elements, and are commonly used deoxidizers in steel. But zirconium element has strong carbon and nitrogen effect, reasonable use not only can play the role of purifying molten steel, but also can modify the carbide. The present application considers to give full play to the deoxidizing effect of rare earth Re and ensure the carbide modification effect of Zr, and controls the total amount of the two elements in the range of 0.02-0.06%.

[0026] P, S as impurity elements seriously damage the plasticity and toughness of the steel, and the content is controlled in the range of ≤0.03%.

[0027] The inventor determines the chemical composition of the wear-resistant and corrosion-resistant alloy steel by comprehensive consideration and experimental verification. Through the appropriate addition of vanadium element and the synergistic addition of zirconium and rare earth elements, the modification of carbide in the wear-resistant and corrosion-resistant steel is realized, and combined with the cooperation of Cr, Ni, Mo and C elements, the wear-resistant and corrosion-resistant alloy steel with high toughness, high wear resistance, high corrosion resistance and good impact resistance is obtained.

[0028] In the optional embodiment, the microstructure of the matrix of the wear-resistant and corrosion-resistant alloy steel includes lath martensite, austenite and modified nanocarbide, and the modified nanocarbide is dispersedly distributed in the lath martensite and the austenite. The austenite is the residual austenite in the matrix, and the austenite in the matrix of the alloy steel of the present application can be transformed into lath martensite after treatment, and the hardness and toughness of the steel are enhanced, and at the same time, part of the residual austenite is retained in the matrix, and the high toughness of the austenite can make the wear-resistant and corrosion-resistant alloy steel have good wear resistance, toughness and corrosion resistance.

[0029] Preferably, the modified nanometer carbide comprises a complex carbide of chromium, vanadium and zirconium. Since the elements are dispersed in the molten steel during the process of smelting, the modified nanometer carbide in the alloy steel is difficult to be a single metal carbide, and is generally a carbide composed of multiple metals. In the present application, Cr, V and Zr can all react with C to precipitate carbides, so the modified nanometer carbide of the present application is a carbide containing chromium, vanadium and zirconium.

[0030] Since the carbides of Cr and V are prone to grow in the matrix, thereby affecting the performance of the steel, in order to prevent the modified nanometer carbide from being too large in size, preferably, the carbide of zirconium in the modified nanometer carbide is precipitated and coated on the outermost layer, which is beneficial to control the size and shape.

[0031] Preferably, the modified nanometer carbide is a spheroid, and the size of the modified nanometer carbide is ≤500 nm. At present, the precipitated carbide in the steel matrix is mostly square particles with obvious edges and corners, which can cause stress concentration and affect the quality of the steel. However, there is no related technical means to solve the problem of stress concentration of the carbide. The present inventors found that adding Zr and Re to the steel for modification can fully exert the carbon affinity of Zr due to the deoxidation protection of Re on Zr, so that the size of the carbide can be effectively controlled and kept within 500 nm, and the shape is a spheroid. Since the spheroid has no obvious edges and corners, the problem of stress concentration of the carbide is solved, and the quality of the steel is improved.

[0032] It should be noted that the modified nanometer carbide is precipitated during the reaction and preparation process, and certainly has an irregular shape. The spheroid described in the present application is relative to square particles with edges and corners, such as tetrahedron and triangular pyramid, and has no obvious edges and corners, and therefore tends to be spherical. It is not meant that the modified nanometer carbide of the present application is completely spherical.

[0033] Preferably, the volume fraction of austenite is 6-12%, and the remaining components of the matrix are lath martensite and modified nanometer carbide. Controlling the volume fraction of austenite in the above range can ensure sufficient conversion of austenite to lath martensite, improve the hardness and toughness of the alloy steel, and at the same time retain part of the residual austenite in the matrix structure. Due to the existence of this high-toughness phase structure, the alloy steel has good wear resistance, toughness and corrosion resistance.

[0034] In an optional embodiment, the erosion-resistant alloy steel has a hardness of ≥55HRC, a non-notch room temperature impact absorption energy of ≥55J, a tensile strength of ≥1600MPa, and a surface passivation film formed in a weakly acidic environment with a pH of ≥4.0, and has good corrosion resistance. The passivation film is mainly composed of oxides of Cr, Fe and Mo, and the above components in the alloy steel have excellent performance in improving the corrosion resistance thereof.

[0035] In a second aspect, the present application provides a method for preparing the carbide-modified erosion-resistant alloy steel according to any one of the preceding embodiments, which comprises smelting raw materials of C, Mn, Cr, Si, Ni, Mo, N and Fe into molten steel in a proportion, then adding raw materials of V for the first smelting modification in a proportion, and adding raw materials of Zr and Re for the second smelting modification in a proportion. After the two smelting modifications, the molten steel is poured into a casting, and the casting is then subjected to heat treatment. It should be noted that S and P are inevitable impurity elements in the raw materials during the smelting process of the steel, and therefore, no raw materials of S and P need to be added during the smelting of the molten steel, and only the contents of S and P need to be controlled during the subsequent smelting process.

[0036] The inventors smelt the molten steel by adopting the method of twice smelting modification. The addition of an appropriate amount of vanadium not only ensures sufficient solid solution strengthening of the steel, but also forms complex carbides with Cr elements in the steel during the solidification process, thereby inducing the precipitation of hard carbide particles. Then, raw materials of Zr and Re are added for the second smelting modification, so as to deoxidize and protect Zr with rare earth Re, thereby fully utilizing the carbonophilic property of Zr to modify the formed carbides. The size and shape of the carbides after such secondary modification can be effectively controlled, thereby improving the strength and hardness of the steel. In addition, the second smelting modification by adding raw materials of Zr and Re can inhibit the growth of the modified nanocarbides, thereby avoiding the formation of crevice corrosion or galvanic corrosion due to the increase of the interface between the carbides and the alloy steel matrix in the corrosion environment. Therefore, the second smelting modification of the present application makes an important contribution to maintaining the overall corrosion resistance of the alloy steel, and is an important guarantee for the performance of the erosion-resistant alloy steel of the present application.

[0037] In an optional embodiment, the heat treatment comprises sequentially subjecting the casting to homogenizing annealing, quenching and tempering.

[0038] Preferably, the homogenizing annealing comprises heating the casting to 620-660℃ at a rate of ≤80℃ / h, then heating to 1060-1120℃ at a rate of 80-120℃ / h, and then cooling in the furnace. During the homogenizing annealing, the control parameters are within the above ranges, which can eliminate the as-cast structure of the casting and make the elements fully diffuse.

[0039] Preferably, the quenching includes heating the cast piece after the homogenizing annealing treatment to 1040-1080℃ at a rate of 80-100℃ / h, and then oil cooling to room temperature. During the quenching, if the temperature is too high, the grains will be coarsened, which will affect the mechanical properties; if the temperature is too low, the temperature gradient during the oil quenching will not be enough, and the carbides will not be completely dissolved into the matrix, and too much residual austenite will be formed, which will affect the properties. In order to ensure that enough martensite is transformed into residual austenite, but the grains are not coarsened significantly, the quenching parameters are controlled in the above range.

[0040] Preferably, the tempering includes heating the cast piece after the quenching treatment to 160-260℃, and then air cooling to room temperature. The low-temperature tempering precipitates tempered martensite, which can ensure that the alloy steel has enough hardness.

[0041] In an optional embodiment, the holding time during the heat treatment is proportional to the thickness of the cast piece, that is, the thicker the cast piece, the longer the holding time.

[0042] Preferably, when the maximum thickness of the cast piece is <50mm, the holding time is the maximum thickness of the cast piece divided by 25 to obtain a value in hours as the holding time; when the maximum thickness of the cast piece is ≥50mm, the holding time is the maximum thickness of the cast piece divided by 20 to obtain a value in hours as the holding time; wherein the unit of the maximum thickness of the cast piece is mm. For example, when the maximum thickness of the cast piece is 50mm, the holding time is 2.5h; when the maximum thickness of the cast piece is 25mm, the holding time is 1h. The holding time obtained by the above method should be the holding time of each time during the heat treatment, for example, when the maximum thickness of the cast piece is 50mm, the holding time during the quenching is 2.5h, the holding time during the tempering is 2.5h, and the holding time during the two annealings is 2.5h.

[0043] In an optional embodiment, the second melting modification includes pouring the molten steel obtained after the first melting modification into a ladle containing raw materials of Zr and Re, and standing until the molten steel cools to the pouring temperature in the ladle. Since Zr is easy to oxidize, long-time melting will cause it to fail to achieve the purpose of controlling the shape and size of carbides, so Zr needs to be added at the end of melting. Similarly, in order to ensure the quality of the molten steel, after adding Zr and Re, it is only necessary to wait for the reaction.

[0044] Preferably, in order to ensure that the molten steel remains in a flowing state and prevents solidification, before pouring the molten steel into the ladle, the ladle is preheated, the preheating temperature of the ladle is ≥500℃, and the preheating time is ≥1h; more preferably, the preheating temperature of the ladle is 500-800℃, and the preheating time is 1-2h.

[0045] Preferably, in order to ensure complete reaction of Zr and Re, the size of the raw material of Zr and Re is less than 2 cm. The raw material is preheated and evenly spread on the bottom of the ladle before the molten steel is poured into the ladle, and the preheating temperature is 150-250℃.

[0046] Preferably, the raw material of Zr is zirconium iron, and the raw material of Re is rare earth iron alloy.

[0047] In an optional embodiment, after the first smelting modification, the temperature of the molten steel is 1580-1620℃.

[0048] Preferably, in order to ensure complete reaction of V, the size of the raw material of V added in the first smelting modification is less than 5 cm.

[0049] Preferably, the time for adding the raw material of V into the molten steel is 5-30 min before the molten steel is poured into the ladle.

[0050] Preferably, the raw material of V includes vanadium iron alloy or vanadium-nitrogen alloy.

[0051] In an optional embodiment, when cast into a casting, the temperature of the molten steel is 1460-1490℃.

[0052] Preferably, when the casting is subjected to heat treatment, the temperature of the casting is ≤200℃. That is, the casting needs to be cooled to ≤200℃ after pouring is completed, and then further heat treatment is performed.

[0053] In a third aspect, the present application provides a use of the carbide-modified corrosion-resistant alloy steel according to any one of the preceding embodiments or the preparation method according to any one of the preceding embodiments in the field of improving the corrosion resistance or friction resistance of equipment.

[0054] Example 1

[0055] The present embodiment provides a carbide-modified corrosion-resistant alloy steel, which comprises, by mass percentage, C: 0.34%, Mn: 0.6%, Cr: 10.5%, Si: 0.6%, Ni: 0.8%, Mo: 0.6%, V: 0.25%, N: 0.01%, Zr: 0.015%, Re: 0.015%, S≤0.03%, P≤0.03%, and the balance of iron and unavoidable impurities.

[0056] The present embodiment also provides a preparation method of the above-mentioned carbide-modified corrosion-resistant alloy steel, comprising the following steps:

[0057] S01, the raw materials such as scrap steel, chromium iron, molybdenum iron, silicon iron, electrolytic manganese, and nickel plate are mixed according to the above alloy content ratio, and then smelted in a medium-frequency induction furnace, and after deoxidization and deslagging, qualified molten steel is obtained.

[0058] S02. Five minutes before tapping, ferrovanadium with a size of less than 5cm is added to the molten steel from step S01 for the first modification treatment. Before tapping, the temperature of the molten steel is raised to 1620℃.

[0059] S03. Preheat the ladle to 500℃ for 1 hour. During the preheating process, thoroughly mix zirconium iron and rare earth iron alloy with a size of less than 2cm and bake them at 200℃. Spread the baked zirconium iron and rare earth iron alloy mixture evenly on the bottom of the preheated ladle. Pour the molten steel from step S02 into the ladle and let it stand for a while until the temperature of the molten steel reaches the pouring temperature.

[0060] S04. The molten steel from step S03 is poured into a casting at 1490℃, with a maximum thickness of 100mm.

[0061] S05. The casting from step S04 is heated to 660°C in a heat treatment furnace at a rate of 80°C / h and held for 5 hours. Then, it is heated to 1120°C at a rate of 100°C / h and held for 5 hours before being cooled to room temperature in the furnace.

[0062] S06. Heat the casting from step S05 to 1080℃ at a rate of 100℃ / h, hold for 5 hours, and then remove from the furnace and quench in oil to room temperature.

[0063] S07. The casting from step S06 is heated to 260℃ at a rate of 80℃ / h, held at that temperature for 5h, and then air-cooled to room temperature to obtain carbide-modified wear-resistant alloy steel.

[0064] The carbide-modified wear-resistant alloy steel provided in this embodiment was observed under a scanning electron microscope, and the results were as follows: Figure 1 The results are shown. (From...) Figure 1 As can be seen, the microstructure of the carbide-modified wear-resistant alloy steel provided in this embodiment consists of lath martensite, austenite, and modified nano-carbide, with the modified nano-carbide dispersed within the lath martensite and austenite. Because Zr and Re are added at the end to modify the molten steel, the surface of the modified nano-carbide in the microstructure has a layer of Zr carbide. Due to the combined effect of Zr and Re, the modified nano-carbide has a spherical shape with no obvious sharp edges, eliminating stress concentration issues. Furthermore, the size of the modified nano-carbide is ≤500nm, ensuring the wear resistance and toughness of the alloy steel.

[0065] The carbide-modified wear-resistant alloy steel provided in this embodiment was examined using an X-ray diffractometer, and the volume fraction of austenite was found to be 8%.

[0066] Example 2

[0067] The embodiment provides a carbide modified erosion-resistant alloy steel, which comprises the following components in percentage by mass: C: 0.27%, Mn: 1%, Cr: 8.5%, Si: 1%, Ni: 0.5%, Mo: 0.8%, V: 0.35%, N: 0.015%, Zr: 0.04%, Re: 0.02%, S≤0.03%, P≤0.03%, and the balance of iron and inevitable impurities.

[0068] The embodiment also provides a preparation method of the carbide modified erosion-resistant alloy steel.

[0069] S01, raw materials such as scrap steel, ferrochrome, ferromolybdenum, ferrosilicon, electrolytic manganese and nickel plate are mixed according to the alloy content proportion, and then are smelted in a medium-frequency induction furnace, and qualified molten steel is obtained after deoxidation and deslagging.

[0070] S02, 5 minutes before tapping, vanadium iron with a size less than 5 cm is added to the molten steel in the step S01 for first modification treatment, and the temperature of the molten steel is increased to 1580 ℃ before tapping.

[0071] S03, the pouring ladle is preheated to 600 ℃, the preheating time is 2 h, and during the preheating process, zirconium iron and rare earth iron alloy with a size less than 2 cm are fully mixed and baked at 200 ℃, the mixed mixture of the baked zirconium iron and the rare earth iron alloy is uniformly spread on the bottom of the preheated pouring ladle, the molten steel in the step S02 is poured into the pouring ladle, and is fully placed until the temperature of the molten steel reaches a pouring temperature.

[0072] S04, the molten steel in the step S03 is poured into a casting at 1460 ℃, and the maximum thickness of the casting is 80 mm.

[0073] S05, the casting in the step S04 is heated to 620 ℃ at a rate of 60 ℃ / h in a heat treatment furnace, is kept for 4 h, is then heated to 1060 ℃ at a rate of 120 ℃ / h, is kept for 4 h, and is cooled to room temperature in a furnace.

[0074] S06, the casting in the step S05 is heated to 1040 ℃ at a rate of 100 ℃ / h, is kept for 4 h, and is oil quenched to room temperature after being taken out of the furnace.

[0075] S07, the casting in the step S06 is heated to 160 ℃ at a rate of 60 ℃ / h, is kept for 4 h, and is air cooled to room temperature after being taken out of the furnace, so that the carbide modified erosion-resistant alloy steel is prepared.

[0076] Embodiment 3

[0077] The embodiment provides a carbide modified erosion-resistant alloy steel, which comprises, in percentage by mass, C: 0.3%, Mn: 0.4%, Cr: 11.5%, Si: 0.7%, Ni: 0.3%, Mo: 0.3%, V: 0.15%, N: 0.006%, Zr: 0.03%, Re: 0.01%, S≤0.03%, P≤0.03%, and the balance of iron and inevitable impurities.

[0078] The embodiment also provides a preparation method of the carbide modified erosion-resistant alloy steel.

[0079] S01, raw materials such as scrap steel, chromium iron, molybdenum iron, silicon iron, electrolytic manganese and nickel plate are mixed according to the alloy content ratio, and then smelting is performed in a medium-frequency induction furnace, and qualified molten steel is obtained after deoxidation and slag removal.

[0080] S02, 5 minutes before tapping, vanadium iron with a size less than 5 cm is added to the molten steel of the step S01 for the first modification treatment, and the temperature of the molten steel is increased to 1600 ℃ before tapping.

[0081] S03, the pouring ladle is preheated to 550 ℃, the preheating time is 1 h, and during the preheating process, zirconium iron and rare earth iron alloy with a size less than 2 cm are fully mixed and baked at 200 ℃, the mixed mixture of the baked zirconium iron and the rare earth iron alloy is uniformly spread on the bottom of the preheated pouring ladle, the molten steel of the step S02 is poured into the pouring ladle, and the molten steel is fully placed until the temperature of the molten steel reaches the pouring temperature.

[0082] S04, the molten steel of the step S03 is poured into a casting at 1480 ℃, and the maximum thickness of the casting is 60 mm.

[0083] S05, the casting of the step S04 is heated to 640 ℃ at a rate of 80 ℃ / h in a heat treatment furnace, and then heated to 1080 ℃ at a rate of 80 ℃ / h, and after being kept for 3 h, the furnace is cooled to room temperature.

[0084] S06, the casting of the step S05 is heated to 1060 ℃ at a rate of 80 ℃ / h, and after being kept for 3 h, the furnace is oil-quenched to room temperature.

[0085] S07, the casting of the step S06 is heated to 220 ℃ at a rate of 60 ℃ / h, and after being kept for 3 h, the furnace is air-cooled to room temperature, and the carbide modified erosion-resistant alloy steel is prepared.

[0086] Comparative Example 1

[0087] The comparative example provides an alloy steel, which is different from the embodiment 1 only in that the V, Zr and Re elements are not contained in the element composition, and the rest of the composition and the preparation method are the same as those of the embodiment 1.

[0088] It can be understood that, since the present comparative example does not add V, Zr and Re elements, after the smelting of S01 step is completed, the pouring of S04 step is directly performed.

[0089] Comparative Example 2

[0090] The present comparative example provides an alloy steel, which is different from Example 1 only in that the element composition contains V: 0.05%, and the rest of the composition and the preparation method are the same as those of Example 1.

[0091] Comparative Example 3

[0092] The present comparative example provides an alloy steel, which is different from Example 1 only in that the element composition does not contain Zr and Re elements, and the rest of the composition and the preparation method are the same as those of Example 1.

[0093] It can be understood that, since the present comparative example does not add Zr and Re elements, after the smelting of S02 step is completed, the pouring of S04 step is directly performed.

[0094] Comparative Example 4

[0095] The present comparative example provides an alloy steel, which is different from Example 1 only in that, in S05 step: after that, the temperature is increased to 1020℃ at a rate of 100℃ / h, and after holding for 5h, the furnace is cooled to room temperature; and in S06 step: the casting of S05 step is heated to 1000℃ at a rate of 100℃ / h, and after holding for 5h, the furnace is oil-quenched to room temperature.

[0096] Comparative Example 5

[0097] The present comparative example provides an alloy steel, which has a chemical composition including, by mass percentage, C: 0.34%, Mn: 0.6%, Cr: 7.0%, Si: 0.6%, Ni: 0.8%, Mo: 0.6%, V: 0.25%, N: 0.01%, Zr: 0.015%, Re: 0.015%, S≤0.03%, P≤0.03%, and the balance being iron and inevitable impurities. It is different from Example 1 only in that the Cr content is low, and the rest of the composition and the preparation method are the same as those of Example 1.

[0098] Comparative Example 6

[0099] The present comparative example provides an alloy steel, which is specifically a wear-resistant and corrosion-resistant alloy steel with a grade of ZGMS120Mn18Cr2 in GB / T 31205 wear-resistant and corrosion-resistant steel castings. The chemical composition is: C: 1.2%, Mn: 17%, Cr: 2%, Si: 0.6%, S≤0.04%, P≤0.06%, and the balance being iron and inevitable impurities. After smelting and casting, the water toughening heat treatment process recommended by the national standard is used for preparation.

[0100] Test Example 1

[0101] The alloy steels provided by Examples 1-3 and Comparative Examples 1-6 were tested for mechanical properties, electrochemical corrosion resistance and erosion resistance according to the following standards, and the test results are shown in Table 1.

[0102] Tensile test was carried out according to GB / T 228-2010 Metallic materials - Tensile test methods.

[0103] Hardness test was carried out according to GB / T 230.1-2018 Metallic materials - Rockwell hardness test.

[0104] Impact toughness was tested according to GB / T 229-2007 Metallic materials - Charpy pendulum impact test method, and the sample was unnotched sample.

[0105] Electrochemical corrosion resistance was tested according to GBT 24196-2009 Metallic and alloy - Corrosion electrochemical test method - Guidelines for constant potential and dynamic potential polarization measurement.

[0106] Erosion resistance was tested according to T / CFA010604.05-2017 Steel material impact corrosion and abrasive wear test method of China Foundry Association Standard. The corrosion resistance of Comparative Example 5 in weak acid solution was 1, and the erosion resistance was 1. The relative corrosion resistance (relative erosion resistance > 1 indicates more corrosion resistance than Comparative Example 5) and the relative erosion resistance (relative erosion resistance > 1 indicates more erosion resistance than Comparative Example 5) of the remaining materials were listed.

[0107] Table 1 Properties of alloy steels

[0108]

[0109]

[0110] From Table 1, it can be seen that the comprehensive mechanical properties, corrosion resistance and erosion resistance of the carbide modified erosion-resistant alloy steel of the embodiments 1-3 of the present application are all obviously superior to those of the comparative examples. The comparative example 1 has no modification of the carbide, and the size of the Cr carbide formed in the matrix is large and the edge has corners, so the wear resistance, corrosion resistance and tensile strength are all poor; the V content of the comparative example 2 is reduced, the solid solution strengthening effect is reduced, and the microstructure refining ability is also reduced, so the impact energy, wear resistance, corrosion resistance and tensile strength of the alloy steel are all poor; the comparative example 3 omits the addition of Zr and Re, and the size of the Cr carbide formed in the matrix is large and the edge has corners, so the wear resistance, corrosion resistance and tensile strength are all poor; the comparative example 4 adjusts the holding temperature of the uniform annealing and quenching, which leads to the segregation of the matrix microstructure of the alloy steel, the failure of the carbide to be dissolved in the matrix and the incomplete martensite transformation, so the impact energy, wear resistance, corrosion resistance and tensile strength are all significantly reduced. The comparative example 5 has a low content of the key element Cr, so the hardness is low and it is difficult to passivate in a weak acid environment to maintain high corrosion resistance.

[0111] The preferred embodiments of the present application have been described above by way of example only, not for the purpose of limiting the present application. As it can be variously changed and modified by those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the protection of the present application.

Claims

1. A carbide-modified erosion-resistant alloy steel, characterized by, The alloy steel includes C: 0.27-0.34%, Mn: 0.4-1.0%, Cr: 8.5-11.5%, Si: 0.6-1.0%, Ni: 0.3-0.8%, Mo: 0.3-0.8%, V: 0.1-0.35%, Zr: 0.01-0.06%, RE: 0.01-0.06%, N≤0.015%, S≤0.03%, P≤0.03%, and the balance of iron and inevitable impurities; and the total mass percentage of Zr and RE is 0.02-0.06%. The microstructure of the base of the alloy steel is composed of lath martensite, austenite and modified nanometer carbide, and the modified nanometer carbide is dispersedly distributed in the lath martensite and austenite. The modified nanometer carbide includes a composite carbide of chromium, vanadium and zirconium. The modified nanometer carbide is spheroid, and the size of the modified nanometer carbide is ≤500 nm. The hardness of the alloy steel is ≥55 HRC, the non-notch room temperature impact absorption energy is ≥55 J, the tensile strength is ≥1600 MPa, and a passivation film can be formed on the surface in a weak acidic environment with pH≥4.

0.

2. The carbide-modified erosion-resistant alloy steel of claim 1, wherein, The volume fraction of the austenite is 6-12%.

3. A method of producing a carbide-modified erosion-resistant alloy steel as claimed in claim 1 or 2, characterized in that, The raw materials of C, Mn, Cr, Si, Ni, Mo, N and Fe are proportioned to smelt into molten steel, then the raw materials of V are proportioned to perform first smelting modification, then the raw materials of Zr and RE are proportioned to perform second smelting modification, after the two smelting modifications are completed, the molten steel is poured into a casting, and then the casting is subjected to heat treatment.

4. The production method according to claim 3, characterized by, The heat treatment includes sequentially performing homogenizing annealing, quenching and tempering treatment on the casting.

5. The preparation method according to claim 4, characterized in that, The homogenizing annealing includes heating the casting to 620-660℃ at a rate of ≤80℃ / h, then heating to 1060-1120℃ at a rate of 80-120℃ / h, and then cooling in the furnace.

6. The preparation method according to claim 4, characterized in that, The quenching includes heating the casting after the homogenizing annealing to 1040-1080℃ at a rate of 80-100℃ / h, and then oil cooling to room temperature.

7. The preparation method according to claim 4, characterized in that, The tempering includes heating the casting after the quenching to 160-260℃, and then air cooling to room temperature.

8. The preparation method according to claim 4, characterized in that, The holding time in the heat treatment process is proportional to the thickness of the casting. When the maximum thickness of the casting is <50 mm, the holding time is the maximum thickness of the casting divided by 25 to obtain a value as the holding time in hours; when the maximum thickness of the casting is ≥50 mm, the holding time is the maximum thickness of the casting divided by 20 to obtain a value as the holding time in hours; wherein the unit of the maximum thickness of the casting is mm.

9. The preparation method according to claim 3, characterized in that, The second smelting modification includes pouring the molten steel obtained after the first smelting modification into a ladle containing raw materials of Zr and RE and standing.

10. The method of claim 9, wherein, Before the molten steel is poured into the ladle, the ladle is also preheated, and the preheating temperature of the ladle is ≥500℃ and the preheating time is ≥1h.

11. The method of claim 10, wherein, The preheating temperature of the ladle is 500-800℃, and the preheating time is 1-2h.

12. The method of claim 9, wherein, The size of the raw material of Zr and RE is less than 2cm, and the raw material is dried, preheated and uniformly spread on the bottom of the ladle before the molten steel is poured into the ladle, and the temperature of the preheating is 150-250℃.

13. The method of claim 12, wherein, The raw material of Zr is zirconium-iron, and the raw material of RE is rare earth-iron alloy.

14. The preparation method according to claim 9, characterized in that, After the first smelting modification, the temperature of the molten steel is 1580-1620℃.

15. The preparation method according to claim 14, characterized in that, The size of the raw material of V is less than 5cm. The time of adding the raw material of V into the molten steel is 5-30min before the molten steel is poured into the ladle. The raw material of V includes vanadium-iron alloy or vanadium-nitrogen alloy.

16. The preparation method according to claim 3, characterized in that, When the molten steel is poured into the castings, the temperature of the molten steel is 1460-1490℃.

17. The method of claim 16, wherein, Before the heat treatment of the castings, the temperature of the castings is ≤200℃.

18. The use of the carbide-modified abrasion-resistant alloy steel according to claim 1 or 2 or the abrasion-resistant alloy steel prepared by the method according to any one of claims 3-17 in the field of improving the corrosion resistance or friction resistance of lifting equipment.

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